134 Trow. — Observations on the Biology and 
of fixing were tried, and the material imbedded in the manner 
found suitable in the case of Saprolegnia. Three months of 
hard work produced no more than one fact of any interest — 
that the young oospores contain two exceptionally large 
nuclei. The condition of the material was such as to render 
a detailed critical study impossible. The difficulty appeared 
to be entirely in passing the fixed material from weak alcohol 
into paraffin. 
The size of the nucleus induced me to endeavour to over- 
come these special difficulties, and in June, 1898, they were 
successfully surmounted, and the record of the subsequent 
study, which almost completely occupied my time during 
the following four months, forms the main subject of this 
communication. It may be stated here that in order to 
avoid collapse and consequent distortion of the very sensitive 
organs of this plant, the greatest possible precautions must 
be exercised. One week was generally devoted to the fixing, 
washing, and dehydrating processes, and another to the 
gradual transference from absolute alcohol to paraffin. I was 
fortunate in having the skilled assistance of an attendant 
in carrying out these laborious processes. The amount of 
work is roughly represented by the fact that thirty-six pure 
cultures were successfully imbedded during this time. 
It was only when the work was approaching completion, 
and after many generations of cultures had passed through 
my hands, that at last I was in a position to determine 
accurately the systematic position of the form chosen for 
study. In all the cultures two kinds of oogonia are to be 
found, the relative proportions of which, however, vary 
between wide limits. The one type has smooth pitted walls ; 
the other is provided with protuberances or spines, due to 
outgrowths of the wall through the pits. These protuberances 
vary much in size — from those which are scarcely visible 
to others as long as the diameter of the oospores. For a long 
time I could not convince myself that I had not before me 
mixed cultures containing at least two species, due to some 
flaw in the method adopted for separation. For ten or more 
